The present invention relates to a heavy-duty power transmission V-belt.
A heavy-duty power transmission V-belt comprising a large number of blocks and a tension member including tension cords and hard rubber is conventionally well known and used in the field of stepless transmission. In this V-belt, power is transmitted between the tension member and the blocks through engagement between convex parts of the blocks and concave parts of the tension member. The respective blocks are fixed on the tension member not through adhesion but through physical engagement in order to secure flexibility of the V-belt.
In this conventional heavy-duty power transmission V-belt, each of the blocks is made form a hard resin material in which a reinforcing member for reinforcing the block is embedded in a manner that at least parts to be engaged with the tension member and parts to be in contact with a groove face of a pulley are made from the resin material. The reinforcing member includes upper and lower beam parts respectively located above and below the tension member and a pillar part for connecting the bases of the upper and lower beam parts.
In heavy-duty power transmission using this belt, however, when stress is repeatedly applied to the base of the upper beam part of the reinforcing member within the block located above the tension member (i.e., on the outer side in a radial direction of the pulley), the upper beam part can be broken at the base thereof. This makes impossible the power transmission by using the belt.
Therefore, as is disclosed in Japanese Laid-Open Utility Model Publication No. 5-3692, the upper beam part of the reinforcing member of the block is proposed to be bent into an arcuate shape so that the center portion thereof can be higher than right and left portions thereof extending in a widthwise direction of the belt. In the proposed reinforcing member, stress applied to the base of the upper beam part can be reduced by the bent of the upper beam part, thereby preventing the breakage thereof.
In the proposed reinforcing member, however, it is necessary to increase the size of the entire reinforcing member when further heavier-duty power transmission is desired. In this case, the block is increased in its weight, and hence, centrifugal tension is increased in drive of the belt around a pulley. Accordingly, there is a fear of early breakage of the tension member.
An object of the invention is reducing stress applied to the base of the upper beam part by appropriately modifying the shape of the reinforcing member embedded in each block, so as to further increase transmission load of the belt without largely increasing the weight of the block.